diff --git a/Data/GraphQL/Execute.hs b/Data/GraphQL/Execute.hs
index 413a3cb..3d60bef 100644
--- a/Data/GraphQL/Execute.hs
+++ b/Data/GraphQL/Execute.hs
@@ -32,7 +32,9 @@ document schema (op :| []) = operation schema op
 document _ _ = error "Multiple operations not supported yet"
 
 operation :: Alternative f => Schema f -> AST.Core.Operation -> f Aeson.Value
-operation schema (AST.Core.Query flds) =
-  Aeson.Object . HashMap.singleton "data"
-             <$> Schema.resolve (NE.toList schema) (NE.toList flds)
-operation _ _ = error "Mutations not supported yet"
+operation schema (AST.Core.Query flds)
+    = Aeson.Object . HashMap.singleton "data"
+    <$> Schema.resolve (NE.toList schema) (NE.toList flds)
+operation schema (AST.Core.Mutation flds)
+    = Aeson.Object . HashMap.singleton "data"
+    <$> Schema.resolve (NE.toList schema) (NE.toList flds)
diff --git a/Data/GraphQL/Parser.hs b/Data/GraphQL/Parser.hs
index 03083d5..fc04595 100644
--- a/Data/GraphQL/Parser.hs
+++ b/Data/GraphQL/Parser.hs
@@ -8,7 +8,6 @@ import Control.Applicative ( Alternative(..)
 import Data.GraphQL.AST
 import Language.GraphQL.Lexer
 import Data.List.NonEmpty (NonEmpty(..))
-import qualified Data.Text as T
 import Text.Megaparsec ( lookAhead
                        , option
                        , try
diff --git a/Language/GraphQL/Lexer.hs b/Language/GraphQL/Lexer.hs
index 2d7e1aa..655be3d 100644
--- a/Language/GraphQL/Lexer.hs
+++ b/Language/GraphQL/Lexer.hs
@@ -38,12 +38,9 @@ import Data.List (dropWhileEnd)
 import Data.Proxy (Proxy(..))
 import Data.Void (Void)
 import Text.Megaparsec ( Parsec
-                       , MonadParsec
-                       , Token
                        , between
                        , chunk
                        , chunkToTokens
-                       , lookAhead
                        , notFollowedBy
                        , oneOf
                        , option
@@ -162,7 +159,7 @@ blockString = between "\"\"\"" "\"\"\"" stringValue
         | not (isWhiteSpace $ T.head x) = acc
         | acc == 0 = T.length x
         | otherwise = min acc $ T.length x
-    removeIndent n [] = []
+    removeIndent _ [] = []
     removeIndent n (x:chunks) = T.drop n x : chunks
 
 -- | Parser for integers.